Summer marks the best time for catching the night time phenomenon known as 'noctilucent cloud', (NLC).  Seen without any optical aid, they make for a wonderful sight during the months ahead.

Taken from a rough translation of the Latin 'night-shining', the clouds appear around two hours after sunset above the northwest horizon or a similar length of time before sunrise above the northeast horizon. 

Noctilucent clouds are formed when sunlight is reflected upon the highest altitude clouds in the Earth's atmosphere, some 50 miles above the surface of the planet, right on the edge of space. 

These mesosphere clouds as they are known contain tiny particles of water-ice, reflecting the sun's light, and generating this night time glow.

The National Wales: Noctilucent clouds. Photo: Mel HughesNoctilucent clouds. Photo: Mel Hughes

Their appearance - captured here by Mel Hughes over Holyhead harbour, and by Allan Trow, Manager at Dark Sky Wales, over the Brecon Beacons - is one of wispy threads of cloud with a pale bluey-tinge to them. 

The National Wales: Noctilucent clouds. Photo: Allan TrowNoctilucent clouds. Photo: Allan Trow

With the first records of their presence dating back to around 1885, the clouds rarely display any other colours, although red and green have been sporadically noted. 

In order to catch a glimpse of noctilucent clouds, position yourself with the best view of the northwest horizon as possible with activity expected around 90 or so minutes after sunset.